Fix section mismatch in free_initmem

WARNING: arch/arc/mm/built-in.o(.text+0x11cc): Section mismatch in reference from
the function free_initmem() to the function .init.text:mmapcode_space_init()

Add __init_refok to free_initmem() definition per upstream Linux code.

Change-Id: I5984c80cc30b6ac8b225f9fc8292d761139d90eb
1 file changed